1. Technical Field
This invention relates to support systems, and more particularly, to systems comprising mattresses, cushions, upholstery padding and the like having a resilient cellular material therein positioned upon an innerspring support system.
2. Description of the Prior Art
Many support systems exist within the art which attempt to provide pressure relief for an individual. A trade-off typically occurs in all such systems between comfort, stability and weight in order to achieve a marketable device. For example, support systems which contain liquid, such as waterbeds and water filled cushions, have various support benefits which are well known. On the other hand, such systems also exhibit many disadvantages. In particular, conventional waterbeds and water filled cushions produce a kind of wave action or rolling motion when in use due to the tendency of water or other liquid inside the system to rush rapidly from one part thereof to another when an individual places his weight thereon, thereby forcing the liquid to flow to another part of the system. Moreover, since the envelope containing the liquid in such a system is typically elastically yieldable, a reaction to an initial liquid surge occurs. This reaction often results in a succession of countersurges within the envelope until the system reaches equilibrium. The described undamped surging and countersurging of the liquid in such systems is annoying to most users thereof. In order to obviate the above mentioned disadvantages, many waterbed manufacturers do not employ liquid displacement in that portion of the system which is intended to support the head and shoulders of the user. Instead, they employ a section of mattressing constructed in the conventional manner utilizing coil springs or other equivalent non-liquid structures. Obviously, this introduces an element of complexity to the manufacturing process and, as well, increased costs. Other manufacturers have attempted to dampen waterbed wave motion in various ways. In U.S. Pat. No. 3,585,356 solid particles, such as Styrofoam.RTM., are disposed in liquid for this purpose. U.S. Pat. No. 3,736,604 uses flap means, as illustrated in FIG. 11 therein.
Saloff et al. describe in U.S. Pat. Nos. 4,942,634 and 4,370,768 (entitled "Damped Fluid Displacement Support System and Method for Making the Same" and "Damped Fluid Displacement Support System," respectively, both of which are assigned to the same assignee as the present invention; the contents of each of which are hereby incorporated herein by reference) substantially completely stable damped liquid displacement support systems. In these systems, a core of resilient liquid absorbent material is disposed within a liquid impervious sealed envelope, the core being saturated with a liquid. When force is applied to the system the liquid within the cell migrates from one portion thereof to another before coming to equilibrium about the applied force. The foam core prevents the liquid from rushing from one region where pressure is applied to another region in the support cell. Thus, movement of the fluid within the cell is "damped". Further, the amount of water available to be displaced within the cell is less than one would find in a conventional system and, therefore, the damped liquid system weighs less than a conventional system.
Notwithstanding the commercial success of this damped system, certain drawbacks inherent in the liquid construction remain. For example, although lighter than preexisting liquid support systems, the jell or water used therein necessarily makes the weight of the system a consideration for many individuals who may wish to own such a device Further, although better than conventional water support systems, a period of time is required before the damped liquid support system achieves equilibrium about an applied force, during which time there may be a feeling of instability in the individual using the system.
Non-liquid filled support systems, such as air filled mattress or cushion cells, are also typically unstable when pressure is applied thereto. In addition, such systems provide pressure relieving support characteristics generally inferior to those available with water filled systems.
Blaha describes in a copending, coassigned U.S. application, Ser. No. 626,485, filed Dec. 12, 1990 (entitled "Damped Air Displacement Support System") damped air displacement support systems. In these systems, a core of partially compressed, flexible cellular material is located within an envelope of flexible material. The compression of the core cellular material is sufficient to establish a partial vacuum within the envelope such that when force is applied to the cell the core instantly seeks equilibrium about that area of the envelope receiving the applied force. The core may be a partially compressed, resilient, gas-absorbent cellular material.
These damped air displacement support systems improve upon the comfort and stability, with less package weight, than preexisting body supporting techniques. The systems instantly contour to a body to provide pressure relief without jeopardizing stability.
While these damped air displacement support systems improve on preexisting support systems, intense efforts continue in this area for interface pressure reduction devices aimed at replacement of the more conventional bedding systems, such as box springs and mattresses. Although many of the preexisting devices have excellent properties, a key element often sacrificed is durability. To its advantage, the conventional innerspring system (for various patented innerspring systems, see Forster, U.S. Pat. No. 4,628,555, issued Dec. 16, 1986; Stumpf, U.S. Pat. No. 4,578,834, issued Apr. 1, 1986; Wagner, U.S. Pat. No. 4,535,978, issued Aug. 20, 1985; and Gurcew and Marcinczyk, U.S. Pat. No. 4,480,823, issued Nov. 6, 1984) has typically four to five times the life of current non-conventional mattress replacements. This relationship of durability can be directly related to cost and in many instances interferes with the sale of the product. Thus, a need exists in the marketplace for an innerspring pressure reducing device which achieves comfort, stability, and superior pressure relieving support, while still providing high durability.